The present invention relates to athletic equipment having a strung surface on which preferred areas for hitting a movable game element can be ascertained, for example, to impart optimal motion thereto or to minimize impact on one's wrist. More particularly, this invention relates to electronic athletic equipment which includes means for indicating when preferred areas of the strung surface have been contacted by the game element.
Generally speaking, sports played with a movable game element and athletic equipment having a strung surface, such as racquets for use in tennis, squash, badminton, etc. require considerable basic skills in order that one may play proficiently and without physical injury. The location at which the movable game element strikes the strung surface of the racquet plays an important role in determining the forces imparted to the game element and the hand, wrist or elbow of a player. For example, if a tennis racquet is swung such that a tennis ball strikes the racquet in approximately the center of the strung surface, then the tennis ball will leave the racquet with optimum velocity and the racquet will not tend to twist in the player's hand. Conversely, if the tennis ball strikes the racquet at a location spaced from the center of the strung surface, the racquet will usually twist the player's hand about the wrist or snap the hand back towards the elbow, so that the ball leaves the racquet at an undesired angle and less than optimum speed. Repeated forces twisting or snapping the hand, wrist and/or elbow resulting from improper contact between racquet and ball may eventually lead to physical injury to the player. Thus, the location on the strung athletic instrument at which contact is made with a movable game element greatly determines the resultant movement of the game element and the reactive forces transmitted to the player.
In order to improve playing ability and minimize the likelihood of injury, a number of devices have been invented to aid in training a player to consistently hit the game element in the center or "sweet spot" of the strung portion of athletic equipment. In general, such prior devices provide audible or visible signals which immediately alert a player ("feedback") when a game element has struck a predesignated portion of the athletic instrument. Unfortunately, such prior devices disadvantageously either require the use of a specially designed racquet and/or special strings, or change the playing characteristics of the racquet in a negative manner.
One such type of prior device comprises metal plates (which noisily clang together upon contact with a ball), a plastic diaphragm, or bead, or the like, which fits or clamps onto the string bed of a racquet for the purpose of signalling when a game element has contacted selected strings. This type of device, seen for example in U.S. Pat. Nos. 4,090,707; 4,141,549 and 4,471,958, actually attaches to one or more racquet strings, thereby interfering with the playing surface area of the racquet and undesirably changing the playing characteristics of the instrument.
Other types of disadvantageous prior devices for alerting a player to the contact of a game element upon predesignated strings require more complex apparatus and specially designed racquets, thereby hindering or eliminating the ability of such a device to be easily retrofit to an existing conventional racquet. Moreover, the manufacturing costs associated with complex devices and/or specially designed racquets is substantially higher. An example of one such prior device is found in U.S. Pat. No. 4,101,132 which utilizes opto-electric sensors built into a racquet frame. Yet another type of prior disadvantageous device for monitoring the impact location of a game element upon a strung surface requires the use of specially coated strings. The problems of providing an impact location monitoring device which is not attached to the playing area of the strings and which is not dependent upon special strings or racquet designs yet remains.
There exists, therefore, a significant need for an improved device that indicates the location at which a game element strikes a strung surface. Such a device is needed which is compatible with, and retrofittable to, a standard racquet using standard strings. Moreover, such a device is needed which does not change the playing characteristics of the racquet, which requires no placement of a load or object directly on the playing area of the strings, and which permits one to chose the size and location of a predetermined strung area that will trigger an indication whenever contacted by a game element. Further, such a device is needed which is lightweight (so that the playing characteristics of a racquet associated therewith remain the same), relatively inexpensive, and which provides an indication of the accuracy with which a player is striking the game element upon the predesignated areas of a strung athletic instrument. The present invention fulfills these needs and provides further related advantages.